The present invention relates to a novel high current ion beam generating apparatus.
U.S. Pat. No. 4,714,860 to Brown et al describes an ion beam generating apparatus which was a significant advance in the field of beams, plasmas and ion beam generation. As noted in the prior art ion beams are quite useful for implanting ions in metals, ceramics, and the like, to change physical characteristics of the same. Where the ion beam is composed of metallic ions the metal vapor vacuum arc source described in the U.S. Pat. No. 4,714,860 has proved to be prolific generator of plasmas containing such ions. Prior proposed ion beam generating apparatuses, including the metal vapor vacuum arc source, utilized convergent wall portions and orifices to direct the plasma plume from the generation region to the extraction region. Unfortunately, although the plasma plume was successfully transported, much of the plasma was wasted or expended in these prior apparatuses. It has been calculated that the maximum efficiency in comparing the ion beam current to the arc current was approximately 0.2% in such prior art devices.
Articles by Limpaecher et al and Ault et al have described confinement of a plasma by a magnetic multipole cusp field produced by a series of ceramic permanent magnets. These prior art magnetic field devices, however, did not consider plasma expansion and ion extraction.
Increasing ion beam current with prior devices requires the increasing of arc current and appurtenant components. In a relatively inefficient system an increase in ion beam current requires a relatively large increase in the sizing of plasma generating components.
An ion source apparatus which is capable of utilizing a metal vapor vacuum arc to produce an ion beam of greatly increased intensity would be a significant advance in the field of ion beam generation.